Free jet stream deflector servovalve



United States Patent 72] Inventors Edward F. McFadden;

Leonard J. Williams, East Aurora, New York [21] Appl. No. 694,739 [22] Filed Dec. 29, 1967 [45] Patented Nov. 24, 1970 [73] Assignee Moog lnc.

East Aurora, New York a corporation of New York [54] FREE JET STREAM DEFLECTOR SERVOVALVE 5 Claims, 16 Drawing Figs.

[52] US. (I 137/83,

a 137/625.63 [51] 1nt.Cl. Fl5c3/12 [50] Field ofSearch 137/83,

, [56] References Cited UNITED STATES PATENTS 3,064,682 11/1962 l-lolzbock 137/83X 3,223,103 12/1965 Trinkler 137/83 3,275,014 9/1966 Plasko 137/81.5 3,399,688 9/1968 Westerman 137/81.5

3,405,727 10/1968 1-li11 .Q

Primary Examiner-Robert G. Nilson Attorney-Sommer, Weber & Gastel fixed receiver passages, thereby to produce a differential fluid output in said passages which is responsive to said signal. The fixed relation of the ejector nozzle and receiver passages is accurately provided by forming wall surfaces thereof in a single member covered on opposite sides by end members, one of which has conduits through which fluid flows with respect to this nozzle and passages and is press-fitted into a recess in the body'of the servovalve to eliminate the need for special sealing means where the fluid is transferred between the valve body and end member. The discharge orifice of the ejector nozzle and the entrance ports to the receiver passages are rectangular to provide linearity of response sensitivity at all times, even around the null position of the deflector because these entrance ports are separated only by an apex ridge which is disposed centrally opposite this discharge orifice. The deflector may also be movable other than transversely of the entrance ports to the receiver passages to vary gain.

I Patntd Nov. 24, 1910 v 3,542,051

Sheet of 3 3o 29' none 3| 25 INVENTORS EDWARD E'McFADDEN LEONARD J. WILLIAMS ATTOR NEYS Pa t en te'd Nov. 24, 1970 3,542,051

Sheet g of3 INVENTORS EDWARD F. McFADDEN LEONARD J. WILLIAMS ATTORNEYS Patented Nov. 24, 1970 3,542,051

I Sheet o f3 v INVENTORS EDWARD F. M: FADDEN LEONARD J. WILLIAMS Q MKW ATTORNEYS 1 FREE JET STREAM DEFLEc'roR-sE-RvovALv BACKGROUND OF THE INVENTION This invention relates to the art of servovalves, particularly those of the 'electrohydraulic typ One well-known'type is disclosed in U.S. Pat. No. 3,228,423 as having a fluid amplifier of the double nozzle-flapper type. Anotherexample of a known servovalve is disclosed in U.S. Pat. No. 2,884,907 as having a fluid amplifier of the movable jet pipe type.

SUMMARY OF THE INVENTION I The present invention relates to a servovalve having a fluid amplifier of an improved construction which provides advantages over servovalves of either the nozzle-flapper type or Before consideringthese advantages it is pointedout that the improved fluid amplifier of the present 'invention'broadly comprisesa-fixed ejector nozzle having a discharge orifice arthe movable jeti'pipe type.

ranged to discharge a free jet stream of fluid, a pair of fixed signal to the stream deflecting member, sometimes hereinafter also referred to as a deflector. v

- Compared to a nozzle-flapper type servovalve, a servovalve having the improved fluid amplifier of the present invention is more efficient in :the respects of having a higher pressure recovery, a higher flow recovery, and can control more hydraulic 'power because of its insensitivity to load forces. Furthermore, the fluid flows and pressures do not develop high forces on the jet stream deflector and therefore a smaller torque motor can be used in the case of an electrical signal input control. Still further, the improved fluid amplifier has a high contamination tolerance since the discharge orifice of the fixed ejector Inozz le of the improved fluid amplifier can be larger than thedischarge'orifices of-the nozzles in the nozzleflapper type-of fluid amplifier. Additionally, the improved fluid amplifier has only a single fluid'inlet whereas the double nozzle-flapper type of fluid amplifier has two fluid inlets because of the two nozzles employed.

Compared to. the movable jet pipe type of fluid amplifier, the improved fluid amplifierof the presentinvention possesses the advantage of having a fixed'ejector nozzle and thereby avoids the mechanical disadvantages attending providing a movable fluid carrying conduit or pipe. Further, the improved fluid amplifierof the present'in'vention provides a predetermined spatial relationship of theejector nozzle tothe receiver passages. By providing the ejector nozzle and receiver passages in a single part in accordance with the present invention the precise geometric arrangement between the ejector nozzle and-receiver passages can be carefully-controlled during manufacturer and alsocan'be tested for acceptability before incorporation in a complete servovalve. Furthermore, the discharge orifice of the ejector nozzle and the entrance ports of the receiver passages of the improved fluid amplifier of the present invention, severally canbe of'rectangular shape which i preferred. Compared to round openings as employed inajet BRIEF DES CRIPTION OF 'I'I-IE DRAWINGS FIG. Us a vertical generally central sectional view ofa single-stage electrohydraulic servovalve having a fluid amplifier constructed in'accordance with the principles of the present invention and constituting one embodiment thereof.

FIG. 2 is a fragmentary exploded perspective view, partly in section, of the torque motor and a fixed subassembly of the improved fluid amplifier shown in FIG. 1.

FIG. 3 is an enlarged exploded perspective view of the subassembly shown in FIG,.2

FIG. 4 is a vertical central sectional view thereof taken on Iine4-4ofFlG.3.; I

FIG. 5 is a'horizontal sectional view thereof taken on line 5-5 of FIG. 4.

' FIG/6 is a fragmentary vertical generally central transverse sectional view of the body and subassembly shown in FIG. 1 on line 6-6 thereof.

FIG. 7 is a fragmentary enlarged vertical sectional view of the subassembly taken on'line77 of FIG. 4 and showing the discharge orifice of the ejector nozzle looking upstream.

FIG. 8 is another fragmentary enlarged vertical sectional view thereof taken on line 8+8 of FIG. 4 and showing the enthe fixed ejector nozzle toward and into fixed receiver passages and through a centrally disposed but movable deflector when no input control signal to the deflector exists, such deflector being intended for movement transversely of as well as longitudinally of the direction of flow of the free fluid jet stream.

' alsodisplaced longitudinally closer to the nozzle, as compared FIG. 10 is a view similar to FIG. 9 but illustrating the condition of the free fluid jet stream with respect to the receiver passages when an input control signal to the deflector causes the same to move transversely to the left. v

FIG. 11 is a view similar to FIG. 10 but depicting the position. of the deflector displaced transversely to the right in response to a different input control signal and showing a different relationship of the free fluid jet stream with respect to the receiver passages.

FIG.'12 is a view similar to FIG. 10 but on a reduced scale and showing the jet stream deflectordisplaced to the left and to its position shown'in FIG. 10, so as to depict an increase in transverse displacement gain for the deflector as it approaches the nozzle.

FIG. 13 is a view similar to. FIG. 12 and showing the jet stream deflector displaced to the left the same transverse distance but also displaced longitudinally closer to the receiver passages so as to depict a decrease in transverse displacement gain for the deflector as it approaches these passages.

FIg. 14 is a vertical generally central sectional view ofa twostage ele'ctrohydraulic servovalve with mechanical feedback between the stages and having a first-stage fluid amplifier constructed in accordance, with the principles of the present invention and constituting another embodiment thereof.

FIG. 15 is a fragmentary exploded perspective view, partly in section and partly schematic, of the torque motor, a fixed subassembly of the improved first-stage fluid amplifier and the output stage valve spool of the servovalve shown in FIG. 14.

FIG. 16 is a fragmentary enlarged horizontal sectional view of the improved fluid amplifier'taken on line 16-16 of FIG. 14 and depicting the flow of a free fluid jet stream from the fixed ejector nozzle toward and into fixed receiver passages and through a centrally disposed deflector when no input control signal to the deflector exists, such deflector being intended for movement only transversely of and not longitudinally in line with the direction of flow of the free fluid jet stream.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGURES 1-13 The single-stage servovalve shown in FIG. 1 comprises a body represented generally by the numeral 15 having a flat upper side 16 and a parallel flat bottom 18, and suitable laterally extending extensions such as indicated at 19 for attachment of the valve body to some suitable support (not shown). Body is shown as having a cylindrical recess 20 having its axis arranged vertically and centrally of the body, such recess being closed at its lower end as indicated at 21 but having an enlarged counterbore 22 at its upper end which opens to upper body surface 16. An annular upwardly facing shoulder 23 is provided by the enlarged counterbore portion 22 with respect to the lower portion of recess 20.

Arranged above body 15 is an electrical torque motor indicated generally by the numeral 24. A cover 25 suitably fastened to body 15 protects torque motor 24. This torque motor may be of any suitable construction such as that disclosed, for example, in US. Pat. No. 3,023,782. As there and here shown, torque motor 24 comprises upper and lower pole pieces 26 and 27, respectively, between which a pair of permanent magnets is arranged, one of which is disclosed partly at 28 in FIG. 2. These pole pieces are separated to provide a pair of air gaps between which severally the opposite ends of an armature 29 are movably arranged. This armature 29 is shown as having each arm surrounded by an electromagnet coil 30 or 31 suitably interconnected electrically to receive an input signal through lead wires 32.

The armature 29 is also shown as supported on the upper end of a vertically disposed cylindrical flexure tube 33 having a thickened and enlarged annular attaching flange 34 at its lower end arranged against body shoulder 23 and secured to body 15 by a plurality of screws 35. The upper end of flexure tube 33 is suitably sealingly secured to the center of armature 29. The intermediate portion of this flexure tube is thin-walled and bendable as a consequence.

Arranged within flexure tube 33 is a deflector member represented generally by the numeral 36. This is a rigid member the upper end of which is suitably sealingly connected to the intermediate portion of armature 29 and the upper end of flexure tube 33 and extends downwardly below the attaching flange 34, as shown in FIG. 2. This deflector 36 is shown as being a cylindrical barlike member the periphery of which is slightly spaced from the internal wall surface of flexure tube 33.

A fixed subassembly or unit represented generally by the numeral 38 and forming part of the improved fluid amplifier is shown as arranged in body recess 20. This subassembly is shown as including an upper member 39, an intermediate member and a lower member 41. These members are formed as hereinafter described and stacked one upon another and suitably joined together as by brazing to form subassembly 38. This subasse'mbly may be fixedly mounted on body 15 in any suitable manner. As shown, this subassembly has a cylindrical exterior and is preferably press-fitted into body recess 20.

Referring to FIGS. 3 and 4, member 40 is a relatively thin, parallel and flat-sided disc or waferlike member formed with a vertical through opening of special configuration and represented generally by the numeral 42. More specifically, opening 42 is shown as formed to provide a central elongated slot or compartment 43 having opposing and spaced-apart flat sidewalls 44 and 45. Extending generally radially outwardly from flat side 44 is a pair of divergent and spaced apart sidewalls 46 which jointly provide a fixed ejector slot or nozzle 48 having a discharge orifice 49 in the plane of wall 44. Opposite nozzle 48, member 40 is formed with a pair of converging flat walls 50 which join to form an apex or vertical ridge 50 lying in the plane of compartment side wall 45. Laterally of each wall 50 and spaced therefrom is another flat wall 51 which is shown as intersecting with compartment wall 45. Each corresponding pair of walls 50 and 51 provides a slot or receiver passage, one of these receiver passages being represented by the numeral 52 and the other by the numeral 53. Receiver passage 52 has an entrance port 54 and the other receiver passage 53 has an entrance port 55, these ports lying in the plane ofcompartment wall 45.

Opening 42 also-has an enlarged cylindrical hole portion 56 which communicatively intersects generally radially with the upstream or radially outer end of ejector nozzle passage 48. This opening 42 is further shown as having an enlarged cylindrical hole portion 58 which intersects communicatively and substantially tangentially with receiver passage 52, and still further has a similar hole portion 59 which similarly joins with the radially outer end of receiver passage 53.

All wall surfaces of opening 42 are parallel, that is, they lie in planes which extend axially of disc-shaped member 40 or perpendicularly to its flat upper surface 40' and its flat and parallel lower surface 40". As illustrated these surfaces are vertically disposed. The centerline or longitudinal axis of ejector passage 48 bisects the included angle between walls 50 and also that between walls 51 of receiver passages 52 and 53. Thus a precisely symmetrical orientation of ejector nozzle 48 and receiver passages 52 and 53 is provided and maintained.

Upper member 39 has a lower flat surface 39" which engages flat surface 40'. Lower member 41 has an upper flat surface 41' which engages surface 40". Members 39 and 41 serve as covers for portions of opening 42 in intermediate member 40 as will be more apparent later herein.

Upper member 39 is shown as provided centrally with a cylindrical recess 60 which extends vertically downwardly from the upper surface 39 of this member for substantially its full height. The lower end of this recess 60 is intercepted by a transverse diametral groove 57 provided in the lower end face 39" of member 39. Groove 57 has parallel, vertical and spaced-apart sidewalls 57' and 57", the spacing between which is exactly the same as that between walls 44 and 45 of compartment 43 in. intermediate member 40.

Lower member 41 is shown as provided centrally with a cylindrical recess 61 which extends vertically upwardly from the lower surface 41" of this member for substantially its full height. The upper end of this recess 61 is intercepted by a transverse diametrical groove 67 provided in upper end face 41' of member 41. This groove 67 has parallel, vertical and spaced-apart sidewalls 67 and 67" the spacing between which is exactly the same as that between walls 44 and 45 of compartment 43 in intermediate member 40.

Groove sidewalls 57' and 67' are vertically alined and parallel with compartment sidewall 44, and groove sidewalls 57" and 67" are vertically alined and parallel with compartment sidewall 45.

Thus, subassembly 38 has a vertical through opening 60, 57, 43, 67, 61 (FIG. 4), which at its upper end communicates with the interior of flexure tube 33 and at its lower end with the lower unoccupied portion of body recess 20.

Upper cover member 39 is shown as formed with a passage 62 (FIG. 4) which leads to lower surface 39" so as to be in registry with hole portion 56 in intermediate member 40, and at its other ends leads to and terminates in a hole 63 in the periphery of member 39. This hole is adapted to communicate with one end of a passage 127 (FIG. 6) provided in body 15, the other end of which passage terminates in lower surface 18 of the body as a pressurized fluid supply port 37.

Body 15 is also suitably formed with a passage 47 (FIG. 6) one end of which leads to and communicates with recess 20, and thereby with recess 61 in lower cover member 41, and the other end of this passage terminates in lower surface 18 of body 15 as a return port 47'.

Upper cover member 39 is also shown as formed with a passage 66 (FIG. 4) which at one end leads to lower surface 39 and registers and communicates with hole portion 58 in intermediate member 40. At its other end passage 66 terminates in a hole 68 in the periphery ofmember 39. Hole 68 is shown as communicating with one end of a passage 69 (FIG. 1) formed in body 15, the other end of which passage terminates in an actuating port 70 in lower surface 18 of the body.

Upper cover member 39 is also shown as formed with a passage 71 (FIG. 3) the lower end of which leads to and terminates in lower surface 39" so as to register and commuother end of thispassage7l-le'ads to and terminates in a hole 72 in the periphery'of member 39. This-hole 72 is shown as communicating with one endfofa passage 73 (FIG. 1) formed in body 15, theother end-of which passageterminates in.

another actuating port 74 in lower surface f the body.

Deflector 36 is shown as having at its lower'enda flattened tip 75'including parallel, and flat opposite sides 76 and 78. Referring to rroiuna: side'76 is adjacentnozzle48 and flat side 78 isadjacent receiver passagesSZ and 53. Deflector. tip 75 is shown as having'a vertically elongated opening 79extending therethrou'ghin the form of a slot which extends upwardly from the lower end of the tip. This opening 79 is defined on its vertical sides by two flat surfaces 80 arid 81 which incline'towardl each other in the direction of flow of a stream S which is discharged from ejector nozzie 48-toward receiver passages 52 and 53, the included angle between these surfaces'preferably being in the 45--60rarige.These inclined surfaces 80 and 81 terminate in straight vertical edges 80'and 81 (FIG. 9) which are parallel to ve'rticaledges 46v (FIG. 7)

of discharge'orifice49 of ejector nozzle 48 and also-parallel to vertical edges 50'.and 51' (FIG; 8) of entrance ports 54 and 55 of receiver passages 52;and53. Vertical'edges80' and 81 are spaced apart at leastasrnuch asthe'sp a'cingbetween edges 46'. Vertical edges 50 and 51 of each.- entrance port are spaced apart more thanfledges 46'ofthe'nozzle orifice. Cornpartment walls 44 and' 45 are spaced apartmore than edges Sti'and 51" of each entranceport. Intermediate member 40 is thicker vertically than the distance between edges 50, and 51' of each entrance port. The vertical length of opening 79 in 'deflector 36 is greater than the "thickness of intermediate member 40.

Deflector 36 extends downwardlythrough passage 60, 57 in upper cover member 39,- through compartment 43 in intermediate member 40 andinto at lea'st groove67 in lower member 41 Deflector tipf7'5is thinner than thewidth of cornpartment 43, is narrower than-the length of this compartment,

, and is arranged therein so that'the opening-JO in this tip rec eives thefentir'ejflow of-free fluidjet stream S -,-which is discharged 'from ejector-noz zle 481 and directed" toward receiver passages 52 and 53.;

It will be seen-from FIGS. 4, 5, 7 and' 8 that the space between'nozzle vertical sidewalls 46, and also the space between each pair of receiver vertical sidewalls 5 0 and 51, is overcovered by lower surface 39" of upper cover member139 and undercovered upper surface 41' of lower cover member 41. As best shown in FIGS. 7*an d 8, discharge orifice 49 of ejector nozzlepd 8,.and entrance ports 54and-f55 of receiver passages' 5 2 and '53, respectively, ,are of vertically deflector 36 andup'sta'nding element 105a're rigidly interconnected, the application 'of control force F'represented by arrow 106 will control'the. movement-in or parallel to plane AA of deflector tip 75 having opening 79- therein with respect to ejector nozzle 48 and receiver passages 52and'53.

Operation (Figures l'l3) sense and magnitude of the signal, cause a pivotal movement ofthe armature-deflector member 29, 36 and thereby cause a displacement of deflector tip 75 in plant T-T (FIG. 9) which is transverse to the direction 82 of flow of fluid-issuing from ejector nozzle 48. Tor'que motor 24 is so constructed that the elongated rectangular shape having inajorvertical edges and minor horizontal edges; all the major edges being parallel to one another and to deflector openingedges-.80 and 81'.

. Deflectorjtip"75 is nee to rnovle longitudinally of elongated compartment 43 in a plane T-T-(FIG. 9);.thismovement directionally being at right angles to the aforementioned major edges. Deflector tip .75 i'salsofree to'move in a perpendicular plane A-A (FIG; 9). t v

x The single-stagevalve disclosed-in FIGS. 1 .13 is'shown as 'incorporatingmean's for displacing deflector-36, permitted by bending of flexuretube 33, in a direction generally alined with the dir'ection'of flow of the fluid-as it issues from ejector nozzle 48 as represented by the arrow 82 (FIG. 9). This alinedinovement is in or parallel to plaiit A-A. Thev purpose of such movement is to alter the displacement gain of deflector 36 as hereinafter explained. t

In order to control movement of deflector 36 in or parallel to plane A-A, suitable sig nal inputmeans are provided. While these may be of any suitable type, such means are shown as including a helicalspring 104 which may be loaded in any suitable manner so as to apply a forceF transverse to plane T-T to an element 105 upstanding from armature 29-and rigidly connected thereto. The direction of force F applied is represented by the arrow 106 in FIG. 2'; lnasmjuchas thearmature29,

amount of displacement of deflector tip-75 will beproportional to the magnitude of the input signal applied to leads 32, and also that the sense of such signal willdetermine the direction ofdeflector'tip displacement in plane T -T, all as is well understood by those skilled in the art. it wili also be un- .derstood that the aforementioned pivotal movementof-the armature-deflector member 36 is about a frictionless pivot 25 provided by the bendable thin wall section of flex-ure tube 33.

It is further assumed that actuating ports70 and 74 are connectedto a'load such as an actuator (not shown), pressure port"37;is connectedtoa supply of pressurized fluid, and return port 47.is connected to fluid drain. This produces a free fluid jet stream S to bedischarged byorifice 49 of ejector nozzle 48 and directed symmetrically toward apeir edge 50' and thereby symmetrically with respect to the entrance ports 54-and55 of receiver passages 52 and 53, respectively.

' It will be seen that with no signal input to torque motor 24 should deflector tip 757tend to displace ineit'her direetion in plane Tj-T the free'fluid jet stream S will. impinge upon one or the other of inclined surface s'80 or 81 andtherebyproduce a' reactive force component in plane T-T tending to recenter the deflector tip. Since this recentering reactive force-component is zero when deflector tip .75is centered andincreases as this tip is displaced, there is a fluid induced spring rate on the-ti'p in plane T-TwThlS fluid induced spring rate is'directly proportional to the pressure drop across the servovalve.

When flexure tube 33' is caused tobend by reason of movement of deflector 36 in plane T-T, the flexure tube exerts a centering force which increases in ratio to deflector displace- ,ment and therefore the flexure tube has a-mechanicai spring rate.

I It will also be seen that as the armature 29 ofthe rigid armature-deflector member 29, 36 moves closer to one or the other of the pole pieces 26 or 27 the magnetomotive attractive effect of the permanent magnets such as magnet 28 of the torque motor increases. Such magnetomotive force-is proportional to armature displacement and hence deflector displace ment, and therefore constitutes a negative force gradient.

it is preferred that the mechanical spring rate offlexure tube '33 is not fully balanced .by the negative forcegradient'of the permanent magnets, thus leaving the flexure tube with a 'net retained stiffness. This net retained stiffnessin a particular servovalve'can'beset by magnetic charge level of the permanent magnetsto give the desired servovalve sensitivity to electrical signal input. I

The forces tending to center deflector 36 by reason of impingement of the free fluid jetsteam S againstone or the other of inclined surfaces 81 is small as compared to the forces resulting from a signal input to torque motor 24. In this manner the position of deflector 36 is related tothe force developed by the electrical control signal input to the torque motor.

Generally speaking, it is preferred to keep the fluid centering force on deflector 36 low because of uncertainties due to fluid turbulence and variations in fluid supply pressure. The fluid centering force in plane T-T is essentially independent of the pressures or flows developed in receiver passages 52-and 53. In other words, the fluid centering force is unaffected by the magnitude or nature of the servovalve fluid power output in receiver passages 52 and 53.

The permanent magnets in the torque motor provide substantially no force gradient on the armature-deflector member for motion in a direction perpendicular to plane T-T; that is, in plane A-A which is in line with the direction of flow of the free fluid jet stream S represented by the arrow 82 (FIG. 9). Flexure tube 33 is sufficiently stiff to resist displacement of deflector 36 in plane A-A sought to be induced solely by impingement of the stream against either of inclined surfaces 80 or 81 on deflector tip 75.

With no signal input so that deflector 36 is centered, it will be seen from FIG. 9 that the free fluid jet stream S impinges apex edge 50' symmetrically which splits the stream into two equal branch streams severally entering receiver passages 52 and 53, thus producing zero differential fluid output therein.

Assuming now that an input control signal to torque motor 24 causes deflector tip 75 to displace in plane T-T from the position shown in FIG. 9 to the left to the position shown in FIG. 10, such leftward position being represented by the arrow 83. Deflector tip 75 operates to guide, direct or deflect the free fluid jet stream S to the left so that splitter edge 50 divides the stream into two unequal branches which severally enter receiver passages 52 and 53. This produces a differential fluid output in receiver ports 53 and 52 with the higher pressure and/or flow being in passage 53 and the lower pressure and/or flow in receiver passage 52.

Through the conduit means 59,71, 72 and 73 the fluid output sensed in receiver passage 53 is applied to actuating port 74. Through the conduit means 58, 66, 68 and 69 the fluid output sensed in receiver passage 52 is applied to the other actuating port 70.

Assume again that the deflector 36 is in a centered position so that its tip 75 is oriented with respect to the ejector nozzle and receiver passages, as depicted in FIG. 9, and then an input control signal is applied to torque motor 24 to cause nozzle tip 75 to displace to the right in the direction of the arrow 84 depicted in FIG. 11. As a consequence the free fluid jet stream S is guided, directed or deflected by deflector tip 75 so that more of this stream enters receiver passage 52 than receiver passage S3.'This produces a differential fluid output in actuating ports 70, 74 such that a higher pressure and/or flow is present in port 70 than in port 74.

From the foregoing, it will be seen that the improved fluid amplifier of the present invention applies a transverse directional change in the momentum vector ofa free fluid jet stream issuing from a fixed nozzle. This momentum directional change is accomplished by momentum interchange between the free fluid jet stream and the controllable deflecting element. Stream control by the deflecting element does not depend upon, nor require, a pressure differential between the upstream and downstream faces of the deflecting element. Stream momentum is converted to pressure in the actuating ports by a momentum change in the receiver passages.

Inasmuch as the displacement of deflector 36 in plane T-T is transverse to jet stream 8, it is herein sometimes referred to as transverse displacement. However, with respect to movement ofdeflector 36 in or parallel to plane AA, herein sometimes referred to as longitudinal displacement, if the direction of magnitude of force F represented by arrow 106 is sufficient to cause the tip of deflector 36 to move closer to ejector nozzle 48, in the direction of arrow 112 as depicted in FIG. 12, while being displaced to the left in the direction of the arrow 113 so as to have a transverse displacement D, it will be seen that the differential fluid output effect of the jet stream S with respect to receiver passages 52 and 53 is increased. In other words, movement of jet deflector 36 closer toward ejector nozzle 48 increases the gain of the servovalve with respect to electrical signal inputs which produce transverse displacement of the deflector.

This deflectors' transverse displacement gain can be altered or modulated as may be desired by causingforce F to effect movement in or parallel to plane A-A of jet deflector 36 closer to the entrance ports to receiver passages 52 and 53, as depicted in FIG. 13, such displacement being represented by the arrow 114, while transverse displacement -to the left an amount D is represented by the arrow 115. The closer deflector 36 is moved toward the entrance ports to receiver ports 52 and 53 the more the servovalve output or gain with respect to transverse deflector displacement is reduced.

Displacement of deflector member 36 in or parallel to plane A-A ineither direction will continue until a force balance is reached between force F and the force exerted by flexure tube 33 in resisting bending in such plane.

It will thus be seen that the gain of the transverse displacement of deflector 36 can be modulated by controlling the longitudinal displacement of this deflector.

FIGURES 14-16 The two-stage servovalve shown in FIG. 14 includes a valve body which is constructed similarly to valve body 15 except that body 85 is also formed to provide an internal slideway or cylindrical bore 86 in which a slide or valve spool 88 is slidably arranged so as to leave spool end chambers 89 and 90. Left end chamber 89 is shown as communicating via passage 91 with hole 72a in the periphery of a subassembly or unit 38a which is similar to subassembly or unit 38. The other end chamber 90 is shown as communicating via passage 92 with a hole 68a in subassembly 38a. Passages 91 and 92 are represented by dot-dash lines in FIG. 13.

Subassembly 38a is identical in all respects to subassembly 38 and therefore similar parts and structural elements are indicated by the same reference numerals except as distinguished by the suffix a.

Valve spool 88 is shown as having a left end lobe 93, a right end lobe 94 and an intermediate lobe 95. The space between lobes 93 and 95 communicates with an actuating port passage 96 in body 85 terminating in an actuating port 98. Similarly, the space between lobes 94 and 95 communicates with another actuating port passage 99 in body 85 terminating in another actuating port 100. Actuating ports 98 and 100 are arranged in the lower surface of body 85 and are represented by dot-dash lines in FIG. 15.

As schematically illustrated in FIG. 15, the lower surface of the valve body is provided with a pressure port 77 and a return port 87. Passages 97 and 107 connect pressure port 77 to metering ports 108 and 109 associated with spool end lobes 93 and 94, respectively. Another passage 110 (FIG. 15) connects pressure port 77 to hole 63a FIG. 14) in subassembly 38a. A metering port 111 is shown in FIG. 14 connected to the lower end of recess 20a in body 85, and this same port schematically is shown in FIG. 15 as connected to return port 87. As is well understood by those skilled in the art, displacement of this valve spool axially of bore 86 from a null or centered position will connect one of the actuating ports 98 and 1.00 to pressure port 77 and the other of these actuating ports to return port 87.

Valve spool 88 constitutes the output or second stage of the two-stage valve shown in FIG. 14. The first stage comprises the improved hydraulic amplifier including the subassembly 38a and a free jet stream deflector 360, the latter having some specific differences from deflector 36' as will now be described.

Mechanical feedback is provided between the first and second stages. This is achieved by a wire spring member 101 suitably fastened at its upper end to the lower end of deflector 36a and having its lower end frictionally constrained to move with valve spool 88. For this purpose, the lower end of wire spring member 101 has a spherical ball 102 arranged to have a rolling contact with the opposing sidewalls of annular groove 103 provided in the center lobe 95. This frictionless contact is explained in greater detail in said US. Pat. No. 3,023,782.

Adjacent its lower end, deflector s'sa. has opposite and I parallel flattened side surfa'ce'sr76a and 78 a. lonnecting these flattened'surfaces is a vertically 'elongatedrectangular through opening 79a which, unlike opening '79, isfully'e nclosed on all of its rectan'gularsides. Otherwise opening 79a is constructed asrepresented by the arrow 2a. The deflector 36a'operates with respect to displacementin plane T'e'l" in the same .manner as previously-describedfor deflector$6 with respect to displacement in planeT-T. However, deflector 36a is not free to move in a plan'efA' A (FIG. 16) which isperpendicularto plane T' T".

iOPFR T N (Figures 14-16) i In the two-stage servovalve FlG S. 14-516) ra relationship different from that in the single-stage serv'ovalveFlGS.11- 13) is desirable between the 'decentering force gradient due to magnetomo'tive effects and the centering forcegradient due primarily to deflection of the fl'exui'e tube. The desired relationship is to produce a, substantial balance between these two force gradients such that a condition near trueratecancellation is achieved. In this way, torques created by electrical signal inputs to the torque motor produce transverse displacement of the deflectoriintil an offsetting torque is'developed by the feedback'wire spring member due to displacement of the second stagespool.

If a suitable electrical controlinput signal is applied to leads 32a to effect movement of deflector 36ri'in plane T'-T', there will be produced "a differential fluid output iii-receiver ports 52a and 53a. This differential outp'iit is then applied-"via passages 91 and 92to spool end chambers and 90,'respecfluid with respect to actua ing ports 98 and 100.

Displacement ofd'efle'ctor' member-36a in plane T'-T' will continue until a terque balance isa'chie'ved between that exerted by feedback spring member 101 and that induced by the control signal to torque motor 2 4a. Operation'ofthe feedback wire spring member is "more fully'ex'plained in said U.S. Pat. No. 3,023,732."

From the foregoing'it will be seen that the form of the invention shown in FIGS. 'is a single stage's'ervovalve having the feature of being ableto modulate the transverse displacement gain of'deflector36, whereas the form of the invention shown in FIGS.,14 -1is a two-stage servovalve whichis unsuited for'incorporatioh of thetransvers'e displacement gain featurerAs to a single st'a'ge' servovalve'fit-may or'riiay not incorporate this transverse displacement gai'n' feature, as desired. lt'is'incorporatecl in trated in FIGS. 1l3." f

the single-stage servovalve illus ill stream, a control signal responsive movable deflector having an openingtherein which receivesthe entire flow of said stream and arranged to deflect said stream relative to said ports, and conduit means for transmitting any differential fluid output'produced in said receiver passages, the improvement which comprises said orifice and ports being severally rectangular in shape and having major and minor edges, said major edges being parallel 'to' one another, and said opening is defined by surfaces which inclinetoward each other in the direction of flow of said stream through said opening and terminate in straight edges which are parallel to said major edges.

2. In a servovalve including means providing a fixed ejector nozzle having a discharge orifice arranged to discharge'a free jet stream of fluid, means providing a pair of fixed receiver pa'ssageshaving entrance ports opposite to and spaced from said nozzle orifice and arranged to be ,impinged by said stream, a controlsignal responsive movable deflector having a'n-opening therein which receives the entire flow of said stream and arranged toideflect said stream relative to said ports, and conduit means for transmitting any differential fluid output produced in .said receiver passages, the improvement which comprises said deflector being controllably movable in a direction transverse-to the direction of flow of said stream and also controllably movable in a direction generally alined with the direction of flow of said stream.

'3. The improvement according to claim 2 which further comprises a flexure tube surrounding said deflector and supporting the same for frictionless pivotal movement in said transverse and'alined directions. I

4. In a 'servovalve having a signal input means and a body having fluid pressure return and actuating ports, means providing a fixed ejector nozzle communicatively connected to saidpressure port and having a discharge orifice arranged to discharge a free jet stream of fluid, means providing a pair of fixed receiver passages severally operatively associated with said actuating ports andhaving entrance portsopposite to and spaced from said orifice and arranged to be'impinged by said stream, means providing a compartment between said orifice While an electricalftorqueinotor is'shown in both erribodi I ments of the invention mprbducetr'ansvje'rs displacement'of,

deflector'36 or 3 6jdl'th'e inpntcontrol signal-for the jet deflector may b'e aspecifically different type of signal; F or example, the control sig'nal'canbe a force exerted by ja spring orjbellows. Likewise, the 'co'ritr'ol'sigiial"input -for' effecting longitudinal displacement of jet deflector 36d can be'pr'oduced other than by spring104, such as by another torque'motor or 'a bellows.

While in both embodiments illustrated the jet deflector is shown as supported on a flexiire tube, any. other suitable support may'beemployed;

We claim: i

1; In a servovalve includingmeans-providing a fixed ejector nozzle having adischargeorific'arranged to'discharge a free jet stream of fluid, means pr oviding'a pair of fixed receiver passages having entrance ports opposite toand spaced from said no'zzle orificeja'nd arranged to be irnpinged 'by said and entrance ports and'communicatively connected to said return port, and a deflector arranged at least partly in said compartment to deflect said stream relative to said entrance ports and operatively associated with said signal input means so as who movablyr'esponsive thereto and having an opening therein which receives the entire flow of said stream, the improvement which comprises said means providing said pair of passages in'cludinga pair of converging passage-defining walls which I join to forman apex ridge disposed centrally opposite sa'id'orifice, said entrance ports beingseverally rectangular in shape and including'said apex ridge as a common edgegand said orifice being rectangular in shape and having edges parallelto said apex ridge.

5. In a'servovalve having signal input means and a body having fluid pressure, return and actuating'ports and also a recess provided byacylindricalwall, the improvement which comprises two end membersand an intermediate member snperimposed upon one another and arranged in said recess, the

intefmediate'one of said members having an opening extend ingtherethrough covered on one side by one of said end members and on the other side by the other of said end members,

said opening being shaped to provide in conjunction with the covering afforded by said end members a fixe'dejector nozzle having a discharge orifice and a pair of fixed receiver passages having entrance ports opposite to and spaced from said orifree, one of said end members having a cylindrical periphery press fitted on said wall and a first supply conduit leading from its periphery to said noz'zle upstream of its said orifice, said.

one of said end members also having a pair of first receiver conduits severally leading from its periphery to said receiverpassag'es downstream of their said entrance ports, said body having 'a second supplyfconduit leading from said pressure port and terminating in said wall and communicating with said first supply conduit, said body further having a pair of second receiver conduits severally operatively associated with said ac-- said receiver passages, and a deflector arranged at least partly in said space to deflect said stream relative to said entrance ports and operatively associated with signal input means so as to be movably responsive thereto and having an opening therein which receives the entire flow of said stream. 

